A conversion LED, which uses a modified regular orthosilicate as a luminescent substance, is known from U.S. Pat. No. 7,489,073.
Stable green luminescent substances, in particular having an emission maximum around 520-540 nm, are hardly available. This makes the use of conversion LEDs in display backlighting more difficult and restricts the optimization of high CRI LEDs or warm-white LEDs. Up to this point, primarily orthosilicates have been used in products as green luminescent substances for this range. These do sometimes have high quantum efficiencies, but display inadequate aging behavior in LEDs.
A nitrido-orthosilicate having the composition AE-2-x-aRExEuaSiO4-xNx (AE=Sr, Ba, Ca, Mg; RE=rare earths, in particular Y and/or La) is known from U.S. Pat. No. 7,489,073. EA or also AE stands for alkaline earth elements here. By incorporating YN and/or LaN, a red shift of the spectral location and typically an improvement of the quantum efficiency of the luminescent substance are achieved. The LED aging behavior of this luminescent substance is already significantly better using the production method described therein than in the case of the conventional orthosilicates or other green sion luminescent substances, for example, Ba3Si6O12N2:Eu.
For many applications, for example, for LCD backlighting, the stability in damp surroundings and at higher temperatures is still not optimal, however.